Beam-induced effects

Nevertheless, one must be aware of the possible discrepancy between the observation in an electron microscope and the real structure of catalysts. The discrepancy may come from (1) using model catalyst, which is different from the real one, (2) electron beam induced effects and (3) conditions in an electron microscope that is very different from the ambient of the activated catalysts. For ex situ investigation, it is important to work with good designed model systems whose catalytic activities can be experimentally measured and care must be taken when relating the observed structure with reactivity of catalysts. 

Another area of SIMS that has received a great deal of attention is the study of simple inorganic salts. Marien and De Pauw (92) have looked at the ion-beam-induced effects in SIMS spectra. It is clear that under high ion fluxes significant damage to the surface occurs, with the resulting complication of the spectrum. FAB, or liquid-matrix SIMS, is free of this effect but has the equivalent complication of reactions with the matrix, as discussed previously. 

ODA presents a different beam induced effect. Small spot XPS analysis across the sample does not show any... 

Ion mass and energy most instruments u.se Ar of 1-10 kcV energy. However. the ion-beam-induced effect on depth resolution is minimal for low-energy ions ([Pg.270]

Theberge, R. Bertrand, M.J. Beam-Induced Dehalogenation in LSIMS Effect of Halogen Type and Matrix Chemistry. J. Mass Spectrom. 1995, 30, 163-171. 

Ordered multilayer deposits of phthalocyanine molecules could be observed by low-energy electron diffraciton with no apparent electron beam induced chemical effects. This appears consistent with the general trend for molecules with highly conjugated electron systems to be more stable under electron bombardment than other organic molecules. 

Ion beam induced ablation is one of the most important electronic excitation effects [1,2]. Ablation phenomena occur both thermally and photochemically in many kinds of materials including polymers and biological systems irradiated by both ion beams and high power laser pulses. The mechanisms of ablation of polymers induced by high density electronic excitation have not been made clear yet. 

Fig. 4.4.2. Comparison of bulk and thin specimens in spatial resolution of X-rays generated and induced effects of incident electron beam. (Saka and Thomas 1982)...

Electron-beam-induced evaporation, in which a stream of electrons is emitted from a hot filament and accelerated into a target of the material to be deposited, is an effective means to deposit Al, Au, Cr, Ti, and most any other metal, again in a high-vacuum system. The added complexity of e-beam systems makes them considerably more expensive than comparable thermal deposition apparatus. 

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